Detailed characterization of semiconductor materials with respect to a number of parameters is required for screening the material prior to using it in semiconductor production. Such characterization helps to increase yields and reduce costs, as well as provide a general tool to improve materials manufacturing processes. One well-recognized parameter is the free-carrier concentration. The most widely-used technique for determining free-carrier concentration in semiconductor materials is the Hall technique. This technique requires that contacts be soldered to the material and yields an average carrier concentration across the sample material. The Hall technique is time-consuming, requires skilled personnel, is likely to contaminate the sample and is not particularly useful with thin surface films. The current state of the art of measuring Faraday rotation which is linearly dependent on the free-carrier concentration in the sample is set forth in U.S. Pat. No. 4,818,881 by Tanton et al. John A. Grisham is a co-inventor in the Tanton patent which describes a high sensitivity infrared polarimeter that measures Faraday rotation in a small area of a semiconductor wafer sample. The Tanton polarimeter uses a beam chopped at a particular frequency which is detected and a signal extracted via a lock-in amplifier referenced to the chopper frequency. The Faraday rotation is obtained as a signal that is directly proportional to the intensity of the laser beam incident upon the detector at the chopper frequency. This provides high signal-to-noise ratio rotation measurements.